How many times will Python run the inside the while loop before exiting? x = 1 y = 1 while y

Question

How many times will Python run the inside the while loop before exiting? x = 1 y = 1 while y < 4: y = y + 2

BlackTom AI · Accepted Answer

A while loop is a pre-test loop: Python evaluates the condition (y < 4) before each iteration and only executes the body when the condition is True.

Relevant concepts:
- The loop condition is checked before each execution.
- The statement y = y + 2 updates y by adding 2 each time the body runs.
- Initial value y = 1; x is unused and does not affect the loop.

Step-by-step reasoning (showing all intermediate steps):
1. Initial state: y = 1.
2. Check condition: is y < 4? 1 < 4 is True. Therefore the body executes for the first time.
   - After body: y = y + 2 → y becomes 1 + 2 = 3. (Count = 1)
3. Next loop check: is y < 4? 3 < 4 is True. Therefore the body executes for the second time.
   - After body: y = y + 2 → y becomes 3 + 2 = 5. (Count = 2)
4. Next loop check: is y < 4? 5 < 4 is False. The loop stops and does not execute the body again.

Thus the body contents run exactly two times.

Why this answer is correct:
- The condition is true for y = 1 and y = 3, giving two iterations. Once y reaches 5 the condition fails and the loop exits. There is no extra hidden iteration because the condition is tested before each execution.

Why the other options are incorrect:
- a. 1: Incorrect because after the first iteration y becomes 3 and the condition is still True, so a second iteration occurs.
- c. 3, d. 4, e. 5: Incorrect because the increment of 2 makes y exceed the threshold after the second execution (y becomes 5), so there are not enough True checks to reach 3 or more iterations.

Conclusion: The loop body runs 2 times; this confirms the correct choice b. 2.

How many times will Python run the <body contents> inside the while loop before exiting? x = 1 y = 1 while y < 4: <body contents> y = y + 2单项选择题

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